Many electronic devices operate using one or more clocks. These clocks are often generated using an oscillator. Many different oscillator types exist and can be implemented in different systems. Typical integrated circuits (ICs) often include one or more on-chip oscillators to develop clock signals. Some such oscillators are formed using resistors and capacitors (so-called RC circuits) that are selected to generate a desired clock frequency. For most systems a stable clock frequency is a requisite for proper operation.
One issue affecting output frequency stability over temperature with existing comparator-based relaxation oscillators is that comparator and logic delay is temperature dependent. The temperature coefficient itself varies from part-to-part mainly due to random variations of transistor threshold voltage (VT) and transistor beta. As a result, the random variations temperature coefficient of each IC is factory trimmed at multiple temperature points, which is extremely costly. Another issue in using a comparator-based oscillator is that comparator and logic delay is supply dependent.